Method and Apparatus For Spine Joint Replacement

ABSTRACT

A prosthesis for the replacement of the cartilaginous structures of a spine motion segment is described. The prosthesis comprises an intervertebral disc prosthesis in combination with a facet joint prosthesis.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.12/262,341 filed Oct. 31, 2008 which is a continuation application ofU.S. application Ser. No. 11/1151,140, filed Jun. 13, 2005 and entitledMETHOD AND APPARATUS FOR SPINE JOINT REPLACEMENT, issued U.S. Pat. No.7,445,635. Which is a continuation of: U.S. application Ser. No.10/090,293, filed Mar. 4, 2002 and entitled METHOD AND APPARATUS FORSPINE JOINT REPLACEMENT, issued U.S. Pat. No. 7,090,698. Which claimsthe benefit of: U.S. Application Ser. No. 60/273,031, filed Mar. 2, 2001and entitled TOTAL SPINE JOINT REPLACEMENT (Attorney's Docket No. MED-3PROV). The disclosures listed above are incorporated herein byreference.

BACKGROUND OF THE INVENTION The Field of the Invention

Traumatic, inflammatory, metabolic, synovial, neoplastic anddegenerative disorders of the spine can produce debilitating pain thatcan have severe socioeconomic and psychological effects.

One of the most common surgical interventions today is arthrodesis, orspine fusion, in which two or more adjacent vertebral bodies are fusedtogether in order to alleviate pain associated with the disc(s) locatedbetween those vertebral bodies. Approximately 300,000 such proceduresare performed annually in the United States alone. Clinical successvaries considerably, depending upon technique and indications, andconsideration must be given to the concomitant risks and complications.

For example, while spine fusion generally helps to eliminate certaintypes of pain, it has also been shown to decrease function by limitingthe range of motion for patients in flexion, extension, axial rotationand lateral bending. Furthermore, it is believed that spine fusioncreates increased stresses on (and, therefore, accelerated degenerationof) adjacent non-fused motion segments. Additionally, pseudoarthrosis,resulting from an incomplete or ineffective fusion, may reduce or eventotally eliminate the desired pain relief for the patient. Also, thefusion device(s) used to effect fusion, whether artificial orbiological, may migrate out of the fusion site, thereby creatingsignificant new problems for the patient.

Recently, attempts have been made to recreate the natural biomechanicsof the spine through the use of an artificial disc. Artificial discs areintended to restore articulation between vertebral bodies so as torecreate the full range of motion normally allowed by the elasticproperties of the natural disc, which directly connects two opposingvertebral bodies. Various artificial discs are described by Stefee etal. in U.S. Pat. No. 5,071,437; Gill et al. in U.S. Pat. No. 6,113,637;Bryan et al. in U.S. Pat. No. 6,001,130; Hedman et al. in U.S. Pat. No.4,759,769; Ray in U.S. Pat. No. 5,527,312; Ray et al. in U.S. Pat. No.5,824,093; Buttner-Janz in U.S. Pat. No. 5,401,269; and Serhan et al. inU.S. Pat. No. 5,824,094; all of which documents are hereby incorporatedherein by reference. Still other artificial discs are known in the art.

Unfortunately, however, artificial discs alone do not adequately addressall of the mechanics of the motion of the spinal column.

In addition to the support axial, torsional and intervertebral disc,posterior elements called the facet joints help to shear loads that acton the spinal column. Furthermore, the facet joints are diarthroidaljoints that provide both sliding articulation and load transmissionfeatures. However, the facet joints can also be a significant source ofspinal disorders and, in many cases, debilitating pain. For example, apatient may suffer from arthritic facet joints, severe facet jointtropism or otherwise deformed facet joints, facet joint injuries, etc.There is currently a lack of good interventions for facet jointdisorders. Facetectomy, or the removal of the facet joints, may providesome relief, but it is also believed to produce significant decreases inthe stiffness of the spinal column (i.e., hyperrnobility) in all planesof motion: flexion and extension, lateral bending, and axial rotation.Furthermore, problems with the facet joints can also complicatetreatments associated with other portions of the spine. By way ofexample, contraindications for artificial discs include arthritic facetjoints, absent facet joints, severe facet joint tropism or otherwisedeformed facet joints.

A superior vertebra with its inferior facets, an inferior vertebra withits superior facets, the intervertebral disc, and seven spinal ligamentstogether comprise a spinal motion segment or functional spine unit. Thespinal motion segment provides complex motion along three orthogonalaxes, both in rotation (lateral bending, flexion and extension, andaxial rotation) and in translation (anterior-posterior, medial-lateral,and cranial-caudal). Furthermore, the spinal motion segment providesphysiological limits and stiffnesses in each rotational andtranslational direction to create a stable and strong column structureto support physiological loads.

As mentioned above, compromised facet joints are a contraindication fordisc replacement, due to the inability of the artificial disc (when usedwith compromised facet joints, or when used with missing facet joints)to properly restore the natural biomechanics of the spinal motionsegment. It would therefore be an improvement in the art to provide aspine implant system that facilitates concurrent replacement of theintervertebral disc and facet joints where both have been compromiseddue to disease or trauma.

U.S. Pat. No. Re. 36,758 (Fitz) discloses an artificial facet jointwhere the inferior facet, the mating superior facet, or both, arecovered with a cap. This cap requires no preparation of the bone orarticular surfaces; it covers, and therefore preserves, the bony andarticular structure. The capping of the facet has several potentialdisadvantages, however. If the facet joint is osteoarthritic, a cap willnot remove the source of the pain. Additionally, at least in the case ofsurface replacements for osteoarthritic femoral heads, the capping ofarticular bone ends has proven to lead to clinical failure by means ofmechanical loosening. This clinical failure is hypothesized to be asequela of disrupting the periosteum and ligamentum teres femoris, bothserving a nutrition delivery role to the femoral head, thereby leadingto avascular necrosis of the bony support structure for the surfacereplacement. It is possible that corresponding problems could developfrom capping the facet. Another potential disadvantage of facet cappingis that in order to accommodate the wide variability in anatomicalmorphology of the facets, not only between individuals but also betweenlevels within the spinal column, a very wide range of cap sizes andshapes is required.

U.S. Pat. No. 6,132,464 (Martin) discloses a spinal facet jointprosthesis that is supported on the lamina (which is sometimes alsoreferred to as the posterior arch). Extending from this supportstructure are inferior and/or superior blades that replace the cartilageat the facet joint. Like the design of the aforementioned U.S. Pat. No.Re. 36,758, the prosthesis of U.S. Pat. No. 6,132,464 generallypreserves existing bony structures and therefore does not addresspathologies which affect the bone of the facets in addition to affectingthe associated cartilage. Furthermore, the prosthesis of U.S. Pat. No.6,132,464 requires a secure mating between the prosthesis and thelamina. However, the lamina is a very complex and highly variableanatomical surface. As a result, in practice, it is very difficult todesign a prosthesis that provides reproducible positioning against thelamina so as to correctly locate the cartilage-replacing blades for thefacet joints.

Another approach to surgical intervention for spinal facets is disclosedin International Patent Publication No. W09848717A1 (Villaret et al.).While this publication teaches the replacement of spinal facets, thereplacement is interlocked in a manner so as to immobilize the joint.

Thus it will be seen that previous attempts to provide facet jointreplacement have proven inadequate.

SUMMARY OF THE INVENTION

One object of the present invention to provide a spine jointreconstruction assembly that replaces the intervertebral disc and one ormore of the facet joints in order to restore the natural biomechanics ofa spinal motion segment.

Another object of the present invention is to provide a method forreconstructing the spine joint by replacing the intervertebral disc andone or more of the facet joints in order to restore the naturalbiomechanics of a spinal motion segment.

Still another object of the present invention is to provide a kit forthe reconstruction of multiple spine joints to replace intervertebraldiscs and facet joints in order to restore the natural biomechanics of aspinal motion segment.

In accordance with the present invention, the preferred embodiment, theintervertebral disc is excised and replaced with an artificial disc.This artificial disc may be a device such as is described by Stefee etal. in U.S. Pat. No. 5,071,437; Gill et al. in U.S. Pat. No. 6,113,637;Bryan et al. in U.S. Pat. No. 6,001,130; Hedman et al. in U.S. Pat. No.4,759,769; Ray in U.S. Pat. No. 5,527,312; Ray et al. in U.S. Pat. No.5,824,093; Buttner-Janz in U.S. Pat. No. 5,401,269; and Serhan et al. inU.S. Pat. No. 5,824,094; all which documents are hereby incorporatedherein by reference. Alternatively, the artificial disc may be someother artificial disc of the sort known in the art.

In addition to replacing the intervertebral disc, at least one of thefacet joints is replaced in accordance with the apparatus and methodsdescribed hereinafter. Alternatively, the facet joints may be replacedas described by Fitz in U.S. Pat. No. Re. 36,758; Martin in U.S. Pat.No. 6,132,464; and/or Villaret et al. in International PatentPublication No. WO 9848717A1, which documents are hereby incorporatedherein by reference. Or one or more of the facet joints may be replacedby other apparatus and methods known in the art.

The present invention has several advantages over the prior art. For onething, the present invention can provide a complete replacement of allof the articulation surfaces of a spine motion segment: theintervertebral disc and the facet joints. Proper disc height is restoredwhile degenerated facet joints and the underlying painful bone isreplaced. The prosthetic disc and prosthetic facet joints work togetherto reproduce the desired physiological range of motion and to providelow friction articulations, so that adjacent motion segments arereturned to physiological levels of stress and strain. Furthermore,osteophytic growth can be concurrently removed, and the artificial discand facet joint prosthesis together reestablish intervertebral andcentral foraminal spaces to ensure decompression of any nerve structure.Thus, all sources of pain, such as pain associated with osteoarthritis,instability, and nerve compression, are removed while restoring fullfunction of the spine motion segment.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and features of the present invention will bemore fully disclosed or rendered obvious by the following detaileddescription of the preferred embodiments of the invention, which is tobe considered together with the accompanying drawings wherein likenumbers refer to like parts and further wherein:

FIG. 1 is a perspective view of a portion of the spine;

FIG. 2 is a dorsal view of the portion of the spine shown in FIG. 1;

FIG. 3 is a lateral view of a spine joint reconstructed in accordancewith one aspect of the present invention;

FIG. 4 is a dorsal view of the facet joint shown in FIG. 3;

FIG. 5 is a perspective view of the implanted left inferior facetprosthesis shown in FIGS. 3 and 4;

FIG. 6 is a perspective view of the left inferior facet prosthesis shownin FIGS. 3 and 4;

FIG. 7 is a cranial view of the implanted left superior facet prosthesisshown in FIGS. 3 and 4;

FIG. 8 is a perspective view of the left superior facet prosthesis shownin FIGS. 3 and 4;

FIG. 9 is a perspective view of an alternate implanted left inferiorfacet prosthesis;

FIG. 10 is a perspective view of an alternate left inferior facetprosthesis;

FIG. 11 is a lateral view of an alternative reconstructed spine joint;

FIG. 12 is a dorsal view of an alternative reconstructed spine joint;

FIG. 13 is a perspective view of the implanted left inferior facetprosthesis shown in FIGS. 11 and 12;

FIG. 14 is a perspective view of the alternative left inferior facetprosthesis shown in FIGS. 11 and 12;

FIG. 15 is a cranial view of the alternative implanted left superiorfacet prosthesis shown in FIGS. 11 and 12;

FIG. 16 is a perspective view of the alternative left superior facetprosthesis shown in FIGS. 11 and 12;

FIG. 17 is a perspective view of an alternate bearing surface for thesuperior facet prosthesis shown in FIG. 16;

FIG. 18 is a perspective view of a spine motion segment;

FIG. 19 is a dorsal view of a bilateral facet joint reconstructed inaccordance with the present invention;

FIG. 20 is a lateral view of the bilateral facet joint prosthesis shownin FIG. 19;

FIG. 21 is a dorsal view of the implanted inferior bilateral facetprosthesis shown in FIGS. 19 and 20;

FIG. 22 is an inferior view of the implanted inferior bilateral facetprosthesis shown in FIGS. 19 and 20;

FIG. 23 is a ventral view of the inferior bilateral facet prosthesisshown in FIGS. 21 and 22;

FIG. 24 is a dorsal view of the implanted superior bilateral facetprosthesis shown in FIGS. 19 and 20;

FIG. 25 is a superior view of the implanted superior bilateral facetprosthesis shown in FIGS. 19 and 20

FIG. 26 is a ventral view of the superior bilateral facet prosthesisshown in FIGS. 24 and 25;

FIG. 27 is a perspective view of an alternative embodiment of thesuperior bilateral facet prosthesis shown in FIGS. 24 and 25;

FIG. 28 is a dorsal view of a two level facet joint replacement;

FIG. 29 is a lateral view of the two level facet joint replacement ofFIG. 28;

FIG. 30 is a dorsal view of the implanted four facet prosthesis shown inFIGS. 28 and 29;

FIG. 31 is a perspective view of the four facet prosthesis shown in FIG.30;

FIG. 32 is a perspective view of an alternative form of inferiorbilateral facet prosthesis;

FIG. 33 is a perspective view of an implanted superior and inferiorunilateral facet prosthesis;

FIG. 34 is a perspective view of the unilateral facet prosthesis shownin FIG. 33;

FIG. 35 is a perspective view of a lumbar vertebra;

FIG. 36 is a perspective view of a novel prosthesis that replaces thelamina, the four facets, the spinous process and the two transverseprocesses of a vertebra;

FIG. 37 is an anterior view of the prosthesis shown in FIG. 36;

FIG. 38 is a perspective view of a vertebra which has been resected toreceive the prosthesis shown in FIG. 36

FIG. 39 is a perspective view of the prosthesis shown in FIG. 36 mountedto the resected vertebra shown in FIG. 38;

FIG. 40 is a dorsal view of the prosthesis shown in FIG. 36 mounted tothe resected vertebra shown in FIG. 38;

FIG. 41 is a lateral view of the prosthesis shown in FIG. 36 mounted tothe resected vertebra shown in FIG. 38;

FIG. 42 is a perspective view of a novel prosthesis that replaces thelamina, the four facets and the spinous process of a vertebra;

FIG. 43 is a perspective view of a novel prosthesis that replaces thelamina, the four facets and the two transverse processes of a vertebra;

FIG. 44 is a perspective view of a novel prosthesis that replaces thelamina and the four facets of a vertebra;

FIG. 45 is a perspective view of a novel prosthesis that replaces thetwo pedicles, the lamina, the four facets, the spinous process and thetwo transverse processes of a vertebra;

FIG. 46 is a lateral view of the prosthesis shown in FIG. 45;

FIG. 47 is an anterior view of the prosthesis shown in FIG. 45;

FIG. 48 is a perspective view of a vertebra which has been resected toreceive the prosthesis shown in FIG. 45;

FIG. 49 is a perspective view showing the prosthesis of FIG. 45 mountedto the resected vertebra shown in FIG. 48;

FIG. 50 is a perspective view of a novel prosthesis that replaces thetwo pedicles, the lamina, the four facets and the spinous process of avertebra;

FIG. 51 is a perspective view of a novel prosthesis that replaces thetwo pedicles, the lamina, the four facets and the two transverseprocesses of a vertebra;

FIG. 52 is a perspective view of a novel prosthesis that replaces thetwo pedicles, the lamina and the four facets of a vertebra; and

FIG. 53 is a perspective view showing an alternative arrangement formounting the prosthesis of FIG. 45 to a vertebra.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Disc Prosthesis andSingle Facet Prosthesis

Referring now to FIGS. 1 and 2, there is shown a superior vertebra 1 andan inferior vertebra 3, with an intervertebral disc 2 located inbetween. Vertebra 1 has superior facets 43, inferior facets 6, posteriorarch 35 and spinous process 46. Vertebra 3 has superior facets 7,inferior facets 44, posterior arch 36 and spinous process 45.

Referring now to FIG. 3, in accordance with one aspect of the presentinvention, the intervertebral disc 2 has been replaced by an artificialdisc AD. This artificial disc AD may be a device such as is described byStefee et al. in U.S. Pat. No. 5,071,437; Gill et al. in U.S. Pat. No.6,113,637; Bryan et al. in U.S. Pat. No. 6,001,130; Hedman et al. inU.S. Pat. No. 4,759,769; Ray in U.S. Pat. No. 5,527,312; Ray et al. inU.S. Pat. No. 5,824,093; Buttner-Janz in U.S. Pat. No. 5,401,269; andSerhan et al. in U.S. Pat. No. 5,824,094; all which documents are herebyincorporated herein by reference. Alternatively, the artificial disc maybe some other artificial disc of the sort known in the art.

In addition to the foregoing, the left inferior facet 6 of vertebra 1has been resected and an inferior facet prosthesis 4 has been attachedto vertebra 1. Similarly, the left superior facet 7 of vertebra 3 hasbeen resected and a superior facet prosthesis 5 has been attached tovertebra 3.

FIG. 4 illustrates a dorsal view of the elements shown in FIG. 3. It canbe appreciated that inferior facet prosthesis 4 replicates the naturalanatomy when compared to the contralateral inferior facet 6 of vertebra1. Similarly, it can be appreciated that superior facet prosthesis 5replicates the natural anatomy when compared to the contralateralsuperior facet 7 of vertebra 3.

Turning now to FIG. 5, a perspective view of vertebra 1 with implantedinferior facet prosthesis 4 is provided. Resection at 31 has removed thenatural inferior facet 6 at the bony junction between the inferior facet6 and the posterior arch 35. In this manner, bone pain associated with adisease, such as osteoarthritis, or trauma may be eliminated as theinvolved bony tissue has been osteotomized.

FIG. 6 illustrates a perspective view of inferior facet prosthesis 4.Surface 8 replicates the natural articular surface of the replacedinferior facet 6. Post 9 provides a means to affix inferior facetprosthesis 4 to vertebra 1. Post 9 is implanted into the interior bonespace of the left pedicle P (FIG. 1) on vertebra 1 and may or may notextend into the vertebral body of vertebra Ito provide additionalstability.

FIG. 7 illustrates a cranial view of vertebra 3 with implanted superiorfacet prosthesis 5. Resection surface 32 represents the bony junctionbetween the natural superior facet 7 and the posterior arch 36.

FIG. 8 illustrates a perspective view of superior facet prosthesis 5.Surface 47 replicates the natural articular surface of the replacedsuperior facet 7. Post 37 provides a means for affixing superior facetprosthesis 5 to vertebra 3. Post 37 is implanted into the interior bonespace of the left pedicle P (FIG. 7) on vertebra 3 and may or may notextend into the vertebral body of vertebra 3 to provide additionalstability.

When the total facet joint is replaced, as shown in FIGS. 3 and 4, thensurface 8 (FIG. 6) articulates with surface 47 (FIG. 8) to recreate thenatural biomechanics of the spine motion segment made up of vertebra 1,vertebra 3, and artificial disc AD.

FIG. 9 illustrates an alternative inferior facet prosthesis 10 which isimplanted into the interior bone space of posterior arch 35. Theinterior bone space is accessed from the resection 31.

FIG. 10 shows details of alternative inferior facet prosthesis 10,including the fin 13 that extends into the interior bone space ofposterior arch 35. Surface 12 replicates the natural articular surfaceof the replaced facet.

If desired, a corresponding fin construction can be used to form aprosthetic superior facet.

The surfaces of post 9 (FIG. 6), post 37 (FIG. 8) and fin 13 (FIG. 10)may or may not include porous coatings to facilitate bone ingrowth toenhance the long term fixation of the implant. Furthermore, such porouscoatings may or may not include osteoinductive or osteoconductivesubstances to further enhance the bone remodeling into the porouscoating.

Referring now to FIG. 11, there is shown a lateral view of a superiorvertebra 14 and an inferior vertebra 16, with an artificial disc ADlocated in between as shown. The left inferior facet of vertebra 14 hasbeen resected and an inferior facet prosthesis 18 has been attached tovertebra 14 by means of a screw fastener 17. Similarly, the leftsuperior facet of vertebra 16 has been resected and a superior facetprosthesis 19 has been attached to vertebra 16 by means of a screwfastener 17.

FIG. 12 illustrates a dorsal view of the elements of FIG. 11. It can beappreciated that inferior facet prosthesis 18 replicates the naturalanatomy when compared to the contralateral inferior facet 22 of vertebra14. Similarly, it can be appreciated that superior facet prosthesis 19replicates the natural anatomy when compared to the contralateralsuperior facet 21 of vertebra 16.

Turning now to FIG. 13, there is provided a perspective view of vertebra14 with implanted inferior facet prosthesis 18. Resection 34 has removedthe natural inferior facet at the bony junction between the inferiorfacet and the posterior arch 48. In this manner, bone pain associatedwith a disease, such as osteoarthritis, or trauma may be eliminatedinasmuch as the involved bony tissue has been osteotomized.

FIG. 14 illustrates a perspective view of inferior facet prosthesis 18.Surface 23 replicates the natural articular surface of the replacedfacet. Flange 25 contacts the pedicle and hole 24 receives a fastener toattach inferior facet prosthesis 18 to vertebra 14.

FIG. 15 illustrates a cranial view of vertebra 16 with implantedsuperior facet prosthesis 19. Resection surface 33 represents the bonyjunction between the natural superior facet and the posterior arch 38.

FIG. 16 illustrates a perspective view of superior facet prosthesis 19.Surface 27 replicates the natural articular surface of the replacedfacet. Flange 39 contacts the pedicle and hole 26 receives a fastener toattach inferior facet prosthesis 19 to vertebra 16.

FIG. 17 illustrates an alternative superior facet prosthesis 40 with anbearing surface 41 that mounts to substrate 42. The bearing surface 41is a biocompatible polymeric material, such as ultra high molecularweight polyethylene. Alternately, the bearing surface can be ceramic,such as zirconia or alumina, or metal. The substrate is a biocompatiblemetal alloy, such as an alloy of titanium, cobalt, or iron.

Disc Prosthesis and Double Facet Prosthesis

Referring next to FIG. 18, there is shown a superior vertebra 1005 andan inferior vertebra 1010, with an intervertebral disc 1015 located inbetween. Vertebra 1005 has superior facets 1020, inferior facets 1025, alamina (also sometimes referred to as a posterior arch) 1030, a spinousprocess 1035, and pedicles 1040. Vertebra 1010 has superior facets 1045,inferior facets 1050, a posterior arch 1055, a spinous process 1060, andpedicles 1065 (only one of which is seen in FIG. 18).

Referring now to FIGS. 19 and 20, in accordance with another aspect ofthe invention, intervertebral disc 1015 has been replaced by anartificial disc AD. This artificial disc AD may be a device such as isdescribed by Stefee et al. in U.S. Pat. No. 5,071,437; Gill et al. inU.S. Pat. No. 6,113,637; Bryan et al. in U.S. Pat. No. 6,001,130; Hedmanet al. in U.S. Pat. No. 4,759,769; Ray in U.S. Pat. No. 5,527,312; Rayet al. in U.S. Pat. No. 5,824,093; Buttner-Janz in U.S. Pat. No.5,401,269; and Serhan et al. in U.S. Pat. No. 5,824,094; all whichdocuments are hereby incorporated herein by reference. Alternatively,the artificial disc may be some other artificial disc of the sort knownin the art.

In addition to the foregoing, the left and right inferior facets 1025 ofvertebra 1005 have been resected at 1070 and a bilateral inferior facetprosthesis 1075 has been attached to vertebra 1005 using screw fasteners1080. Similarly, the left and right superior facets 1045 of vertebra1010 have been resected at 1082 (FIG. 24) and a bilateral superior facetprosthesis 1085 has been attached to vertebra 10 using screw fasteners1090.

In FIG. 20 it can be appreciated that bilateral inferior facetprosthesis 1075 replicates the natural anatomy when compared to theintact inferior facets 1025 of vertebra 1005 (FIG. 18). Furthermore,bilateral facet prosthesis 1075 extends from its attachment point in amanner that does not require contact with, or mating to, the complexgeometry of the lamina (or posterior arch) 1030. Resection surfaces 1070provide adequate clearance for bilateral inferior facet prosthesis 1075and provide complete removal of the diseased or traumatized naturalinferior facets 1025.

FIGS. 21 and 22 illustrate how the geometry of the bridge 1095 ofbilateral inferior facet prosthesis 1075 matches that of the posteriorarch 1030 of vertebra 1005 in order to provide adequate clearance forthe central foramen 1100. Articular surfaces 1105 articulate with theopposing superior facets 1045 (or their prosthetic replacements) of thevertebra 1010.

FIG. 23 illustrates the bilateral inferior facet prosthesis 1075 withflanges 1110 that abut against the pedicle 1040 of vertebra 1005. Bridge1095 connects the articular surfaces 1105. Holes 1115 allow theattachment of bilateral inferior facet prosthesis 1075 to vertebra 1005by means of screw fasteners 1080. Alternatively, screw fasteners 1080could be replaced with staples, pins, tacks, anchors, modular fixationposts, or the like. These alternative fasteners could further includeporous coatings to further enhance bony fixation, and could also includeosteoconductive or osteoinductive substances.

In FIG. 24 it can be appreciated that bilateral superior facetprosthesis 1085 replicates the natural anatomy when compared to theintact superior facets 1045 of vertebra 1010. Furthermore, bilateralfacet prosthesis 1085 extends from its attachment point in a manner thatdoes not require contact with, or mating to, the complex geometry of thelamina (or posterior arch) 1055. Resection surfaces 1082 provideadequate clearance for bilateral superior facet prosthesis 1085 andprovide complete removal of the diseased or traumatized natural superiorfacets 1045.

FIG. 25 illustrates how the geometry of the bridge 1120 of bilateralsuperior facet prosthesis 1085 matches that of the posterior arch 1055of vertebra 1010 in order to provide adequate clearance for the centralforamen 1125. Articular surfaces 1130 articulate with the opposinginferior facets of the vertebra 1005.

FIG. 26 illustrates the bilateral superior facet prosthesis 1085 withflanges 1135 that abut against the pedicles 1065 of vertebra 1010.Bridge 1120 connects the articular surfaces 1130 (seen in FIG. 25 butnot seen in FIG. 26). Holes 1140 allow the attachment of bilateralsuperior facet prosthesis 1085 to vertebra 1010 by means of screwfasteners 1090.

FIG. 27 illustrates an alternative superior facet prosthesis 1085A witha bearing surface 1130A that mounts to substrate 1131A. The bearingsurface 1130A is preferably a biocompatible polymeric material, such asultra high molecular weight polyethylene. Alternately, the bearingsurface 1130A can be ceramic, such as zirconia or alumina. The substrate1131A is preferably a biocompatible metal alloy, such as an alloy oftitanium, cobalt, or iron.

FIG. 28 illustrates a superior vertebra 1145, a middle vertebra 1150,and an inferior vertebra 1155. Superior facet prosthesis 1085articulates with quad-facet prosthesis 1160 to recreate the naturalbiomechanics of the replaced facet joints. Inferior facet prosthesis1075 articulates with quad-facet prosthesis 1160 to recreate the naturalbiomechanics of the replaced facet joints at the next upper level. Thus,FIG. 28 illustrates a two level reconstruction of facet joints. Superiorfacet prosthesis 1085, quad-facet prosthesis 1160, and inferior facetprosthesis 1075 are each attached to bone by means of screw fasteners1165.

In the lateral view of FIG. 29, it can be appreciated that superiorfacet prosthesis 1085, quad-facet prosthesis 1160, and inferior facetprosthesis 1075 do not encroach into the intervertebral foraminal spaces1167 where nerve roots extend laterally from the spinal cord.

Referring next to FIG. 30, it should be appreciated that superior bridge1170 and inferior bridge 1175 of quad-facet prosthesis 1160 do notcontact any portion of the lamina 1152 of vertebra 1150. Mounting holes1180 (shown in FIG. 31) are used to secure the flanges 1185 against thepedicles of vertebra 1150.

In FIG. 32, an alternative inferior bilateral facet prosthesis 1190 ispresented. To further stabilize the implant and to counter moments thatact upon the two points of fixation into the pedicles, a set of parallelflanges 1195 extend posteriorly such that the two flanges straddle thespinous process 1035. A bolt 1200 is used to fasten the parallel flangesto the spinous process. Alternatively, other adjunctive structuralfeatures could be added to further stabilize the prosthesis. Forexample, a strut that extends, and attaches, to the transverse processcould be used to further stabilize the prosthesis.

Looking next at FIGS. 33 and 34, there is shown a superior and inferiorunilateral facet prosthesis 1300. Unilateral facet prosthesis 1300comprises a body 1305 and a stem 1310 extending out of body 1305. Asuperior element 1315 extends vertically upward from body 1305, and aninferior element 1320 extends vertically downward from body 1305.Unilateral facet prosthesis 1300 is configured so that when its stem1310 extends into the pedicle of vertebra 1325, superior element 1315will replace a resected superior facet, and inferior element 1320 willreplace a resected inferior facet. If desired, stem 1310 could bereplaced with a screw extending through a hole in body 1305 and into thepedicle.

Disc Prosthesis and Quadruple Facet Prosthesis

Referring next to FIG. 35, there is shown a natural lumbar vertebra 2005comprising a natural vertebral body 2010, a pair of natural pedicles2015 extending from natural vertebral body 2010, a natural lamina 2020extending from natural pedicles 2015, a pair of natural superior facets2025 extending from natural pedicles 2015 and natural lamina 2020, apair of natural inferior facets 2030 extending from natural lamina 2020,a natural spinous process 2035 extending from natural lamina 2020, and apair of natural transverse processes 2040 extending from naturalpedicles 2015.

In accordance with another aspect of the invention, the intervertebraldisc on one side or the other of vertebral body 2010 is replaced by anartificial disc. This artificial disc may be a device such as isdescribed by Stefee et al. in U.S. Pat. No. 5,071,437; Gill et al inU.S. Pat. No. 6,113,637; Bryan et al. in U.S. Pat. No. 6,001,130; Hedmanet al. in U.S. Pat. No. 4,759,769; Ray in U.S. Pat. No. 5,527,312; Rayet al. in U.S. Pat. No. 5,824,093; Buttner-Janz in U.S. Pat. No.5,401,269; and Serhan et al. in U.S. Pat. No. 5,824,094; all whichdocuments are hereby incorporated herein by reference. Alternatively,the artificial disc may be some other artificial disc of the sort knownin the art.

In addition to the foregoing, and looking next at FIGS. 36 and 37, thereis shown a novel prosthesis 2100 which is adapted to replace the naturallamina 2020, the two natural superior facets 2025, the two naturalinferior facets 2030, the natural spinous process 2035, and the twonatural transverse processes 2040. To this end, prosthesis 2100comprises a pair of prosthetic mounts 2115, a prosthetic lamina 2120extending from prosthetic mounts 2115, a pair of prosthetic superiorfacets 2125 extending from prosthetic mounts 2115 and prosthetic lamina2120, a pair of prosthetic inferior facets 2130 extending fromprosthetic lamina 2120, a prosthetic spinous process 2135 extending fromprosthetic lamina 2120, and a pair of prosthetic transverse processes2140 extending from prosthetic mounts 2115.

In the use of prosthesis 2100, natural lumbar vertebra 2005 is resectedat its natural pedicles 2015 so as to remove the natural lamina 2020,the two natural superior facets 2025, the two natural inferior facets2030, the natural spinous process 2035, and the two natural transverseprocesses 2040, leaving a pair of pedicle end surfaces 2041 (FIG. 38).Then the prosthesis 2100 may be attached to the natural pedicles 2015,e.g., by placing prosthetic mounts 2115 against pedicle surfaces 2041and then passing screws 2145 through screw holes 2147 and into naturalpedicles 2015, as shown in FIGS. 39-41. As seen in the drawings, therelative size, shape and positioning of the prosthetic lamina 2120, thetwo prosthetic superior facets 2125, the two prosthetic inferior facets2130, the prosthetic spinous process 2135, and the two prosthetictransverse processes 2140 essentially mimic the relative size, shape andpositioning of the natural lamina 2020, the two natural superior facets2025, the two natural inferior facets 2030, the natural spinous process2035, and the two natural transverse processes 2040, whereby toeffectively restore the vertebra. If desired, holes 2150 may be providedin the prosthetic spinous process 2135 and/or the two prosthetictransverse processes 2140 so as to facilitate re-attaching soft tissueto these structures.

Looking next at FIG. 42, there is shown a novel prosthesis 2200 which isadapted to replace natural lamina 2020, the two natural superior facets2025, the two natural inferior facets 2030, and natural spinous process2035. To this end, prosthesis 2200 comprises a pair of prosthetic mounts2215, a prosthetic lamina 2220 extending from prosthetic mounts 2215, apair of prosthetic superior facets 2225 extending from prosthetic mounts2215 and prosthetic lamina 2220, a pair of prosthetic inferior facets2230 extending from prosthetic lamina 2220, and a prosthetic spinousprocess 2235 extending from prosthetic lamina 2220.

In the use of prosthesis 2200, natural lumbar vertebra 2005 is resectedat its natural pedicles 2015 so as to remove the natural lamina 2020,the two natural superior facets 2025, the two natural inferior facets2030, the spinous process 2035 and the two natural transverse processes2040, leaving a pair of pedicle surfaces 2041 (FIG. 38). Then theprosthesis 2200 may be attached to the natural pedicles 2015, e.g., byplacing prosthetic mounts 2215 against pedicle surfaces 2041 and thenpassing screws 2145 through holes 2247 and into natural pedicles 2015.As seen in the drawing, the relative size, shape and positioning ofprosthetic lamina 2220, the two prosthetic superior facets 2225, the twoprosthetic inferior facets 2230, and the prosthetic spinous process 2235essentially mimic the relative size, shape and positioning of thenatural lamina 2020, the two natural superior facets 2025, the twonatural inferior facets 2030, and the natural spinous process 2035,whereby to effectively restore the vertebra. If desired, holes 2150 maybe provided in the prosthetic spinous process 2235 so as to facilitatere-attaching soft tissue to this structure.

Looking next at FIG. 43, there is shown a novel prosthesis 2300 which isadapted to replace the natural lamina 2020, the two natural superiorfacets 2025, the two natural inferior facets 2030, and the two naturaltransverse processes 2040. To this end, prosthesis 2300 comprises a pairof prosthetic mounts 2315, a prosthetic lamina 2320 extending fromprosthetic mounts 2315, a pair of prosthetic superior facets 2325extending from prosthetic mounts 2315 and prosthetic lamina 2320, a pairof prosthetic inferior facets 2330 extending from prosthetic lamina2320, and a pair of prosthetic transverse processes 2340 extending fromprosthetic mounts 2315.

In the use of prosthesis 2300, natural lumbar vertebra 2005 is resectedat natural pedicles 2015 so as to remove natural lamina 2020, the twonatural superior facets 2025, the two natural inferior facets 2030, thenatural spinous process 2035 and the two natural transverse processes2040, leaving a pair of pedicle surfaces 2041 (FIG. 38). Then theprosthesis 2300 may be attached to the natural pedicles 2015, e.g., byplacing prosthetic mounts 2315 against pedicle surfaces 2041 and thenpassing screws 2145 through holes 2347 and into natural pedicles 2015.As seen in the drawing, the relative size, shape and positioning of theprosthetic lamina 2320, the two prosthetic superior facets 2325, the twoprosthetic inferior facets 2330, and the two prosthetic transverseprocesses 2340 essentially mimic the relative size, shape andpositioning of the natural lamina 2020, the two natural superior facets2025, the two natural inferior facets 2030, and the two naturaltransverse processes 2040, whereby to effectively restore the vertebra.If desired, holes 2150 may be provided in the two prosthetic transverseprocesses 2340 so as to facilitate re-attaching soft tissue to thesestructures.

Looking next at FIG. 44, there is shown a novel prosthesis 2400 which isadapted to replace the natural lamina 2020, the two natural superiorfacets 2025, and the two natural inferior facets 2030. To this end,prosthesis 2400 comprises a pair of prosthetic mounts 2415, a prostheticlamina 2420 extending from prosthetic mounts 2415, a pair of prostheticsuperior facets 2425 extending from prosthetic mounts 2415 andprosthetic lamina 2420, and a pair of prosthetic inferior facets 2430extending from prosthetic lamina 2420.

In the use of prosthesis 2400, natural lumbar vertebra 2005 is resectedat pedicles 2015 so as to remove the natural lamina 2020, the twonatural superior facets 2025, the two natural inferior facets 2030, thenatural spinous process 2035, and the two natural transverse processes2040, leaving a pair of pedicle surfaces 2041 (FIG. 38). Then theprosthesis 2400 may be attached to the natural pedicles 2015, e.g., byplacing prosthetic mounts 2415 against pedicle surfaces 2041 and thenpassing screws 2145 through holes 2447 and into natural pedicles 2015.As seen in the drawing, the relative size, shape and positioning ofprosthetic lamina 2420, the two prosthetic superior facets 2425, and thetwo prosthetic inferior facets 2430 essentially mimic the relative size,shape and positioning of the natural lamina 2020, the two naturalsuperior facets 2025 and the two natural inferior facets 2030, wherebyto effectively restore the vertebra.

Looking next at FIGS. 45-47, there is shown a novel prosthesis 2500which is adapted to replace a pair of natural pedicles 2015, the naturallamina 2020, the two natural superior facets 2025, the two naturalinferior facets 2030, the natural spinous process 2035, and the twonatural transverse processes 2040. To this end, prosthesis 2500comprises a pair of prosthetic pedicles 2515, a prosthetic lamina 2520extending from prosthetic pedicles 2515, a pair of prosthetic superiorfacets 2525 extending from prosthetic pedicles 2515 and prostheticlamina 2520, a pair of prosthetic inferior facets 2530 extending fromprosthetic lamina 2520, a prosthetic spinous process 2535 extending fromprosthetic lamina 2520, and a pair of prosthetic transverse processes2540 extending from prosthetic pedicles 2515.

In the use of prosthesis 2500, natural lumbar vertebra 2005 is resectedat the bases of natural pedicles 2015 so as to remove to two naturalpedicles 2015, the natural lamina 2020, the two natural superior facets2025, the two natural inferior facets 2030, the natural spinous process2035, and the two natural transverse processes 2040, leaving a vertebralbody end face 2042 (FIG. 48). Then the prosthesis 2500 may be attachedto the natural vertebral body 2010, e.g., by placing prosthetic pedicles2515 against vertebral body end face 2042 and then passing screws 2145through holes 2547 and into natural vertebral body 2010, as shown inFIG. 49. As seen in the drawings, the relative size, shape andpositioning of the two prosthetic pedicles 2515, the prosthetic lamina2520, the two prosthetic superior facets 2525, the two prostheticinferior facets 2530, the prosthetic spinous process 2535, and the twoprosthetic transverse processes 2540 essentially mimic the relativesize, shape and positioning of the two natural pedicles 2015, thenatural lamina 2020, the two natural superior facets 2025, the twonatural inferior facets 2030, the natural spinous process 2035, and thetwo natural transverse processes 2040, whereby to effectively restorethe vertebra. If desired, holes 2150 may be provided in prostheticspinous process 2535 and the two prosthetic transverse processes 2540 soas to facilitate re-attaching soft tissue to these structures.

Looking next at FIG. 50, there is shown a novel prosthesis 2600 which isadapted to replace the two natural pedicles 2015, the natural lamina2020, the two natural superior facets 2025, the two natural inferiorfacets 2030, and the natural spinous process 2035. To this end,prosthesis 2600 comprises a pair of prosthetic pedicles 2615, aprosthetic lamina 2620 extending from prosthetic pedicles 2615, a pairof prosthetic superior facets 2625 extending from prosthetic pedicles2615 and prosthetic lamina 2620, a pair of prosthetic inferior facets2630 extending from prosthetic lamina 2620, and a prosthetic spinousprocess 2635 extending from prosthetic lamina 2620.

In the use of prosthesis 2600, natural lumbar vertebra 2005 is resectedat the bases of natural pedicles 2015 so as to remove the two naturalpedicles 2015, the natural lamina 2020, the two natural superior facets2025, the two natural inferior facets 2030, the natural spinous process2035 and the two natural transverse processes 2040, leaving a vertebralbody end face 2042 (FIG. 48). Then the prosthesis 2600 may be attachedto the natural vertebral body 2010, e.g., by placing prosthetic pedicles2615 against vertebral body end face 2042 and then passing screws 2145through holes 2647 and into natural vertebral body 2010. As seen in thedrawing, the relative size, shape and positioning of the two prostheticpedicles 2615, the prosthetic lamina 2620, the two prosthetic superiorfacets 2625, the two prosthetic inferior facets 2630, and the prostheticspinous process 2635 essentially mimic the relative size, shape andpositioning of the two natural pedicles 2015, the natural lamina 2020,the two natural superior facets 2025, the two natural inferior facets2030, and the natural spinous process 2035, whereby to effectivelyrestore the vertebra. If desired, holes 2150 may be provided inprosthetic spinous process 2635 so as to facilitate re-attaching softtissue to this structure.

Looking next at FIG. 51, there is shown a novel prosthesis 2700 which isadapted to replace the two natural pedicles 2015, the natural lamina2020, the two natural superior facets 2025, the two natural inferiorfacets 2030, and the two natural transverse processes 2040. To this end,prosthesis 2700 comprises a pair of prosthetic pedicles 2715, aprosthetic lamina 2720 extending from prosthetic pedicles 2715, a pairof prosthetic superior facets 2725 extending from prosthetic pedicles2715 and prosthetic lamina 2720, a pair of prosthetic inferior facets2730 extending from prosthetic lamina 2720, and a pair of prosthetictransverse processes 2740 extending from prosthetic pedicles 2715.

In the use of prosthesis 2700, natural lumbar vertebra 2005 is resectedat the bases of natural pedicles 2015 so as to remove the two naturalpedicles 2015, the natural lamina 2020, the two natural superior facets2025, the two natural inferior facets 2030, the natural spinous process2035, and the two natural transverse processes 2040, leaving a vertebralbody end face 2042 (FIG. 48). Then the prosthesis 2700 may be attachedto the natural vertebral body 2010, e.g., by placing prosthetic pedicles2715 against vertebral body end face 2042 and then passing screws 2145through holes 2747 and into vertebral body 2010. As seen in the drawing,the relative size, shape and positioning of the two prosthetic pedicles2715, the prosthetic lamina 2720, the two natural pedicles 2015, thenatural lamina 2020, the two natural superior facets 2025, the twonatural inferior facets 2030, and the two natural transverse processes2040, whereby to effectively restore the vertebra. If desired, holes2150 may be provided in the two prosthetic transverse processes 2740 soas to facilitate re-attaching soft tissue to these structures.

Looking next at FIG. 52, there is shown a novel prosthesis 2800 which isadapted to replace the two natural pedicles 2015, the natural lamina2020, the two natural superior facets 2025, and the two natural inferiorfacets 2030. To this end, prosthesis 2800 comprises a pair of prostheticpedicles 2815, a prosthetic lamina 2820 extending from prostheticpedicles 2815, a pair of prosthetic superior facets 2825 extending fromprosthetic pedicles 2815 and prosthetic lamina 2820, and a pair ofprosthetic inferior facets 2830 extending from prosthetic lamina 2820.

In the use of prosthesis 2800, natural lumbar vertebra 2005 is resectedat the bases of natural pedicles 2015 so as to remove the two naturalpedicles 2015, the natural lamina 2020, the two natural superior facets2025, the two natural inferior facets 2030, the natural spinous process2035, and the two natural transverse processes 2040, leaving a vertebralbody end face 2042 (FIG. 48). Then the prosthesis 2800 may be attachedto natural vertebral body 2010, e.g., by placing prosthetic pedicles2715 against vertebral body end face 2042 and then passing screws 2145through holes 2847 and into natural vertebral body 2010. As seen in thedrawing, the relative size, shape and positioning of the two prostheticpedicles 2815, the prosthetic lamina 2820, the two prosthetic superiorfacets 2825, and the two prosthetic inferior facets 2830 essentiallymimic the relative size, shape and positioning of the two naturalpedicles 2015, the natural lamina 2020, the two natural superior facets2025, and the two natural inferior facets 2030, whereby to effectivelyrestore the vertebra.

It should also be appreciated that prostheses 2100, 2200, 2300, 2400,2500, 2600, 2700 and 2800 may be attached to natural vertebra 2005 withapparatus other than the screws 2145 discussed above. Thus, for example,prostheses 2100, 2200, 2300, 2400, 2500, 2600, 2700 and 2800 may beattached to natural vertebra 2005 with rods or posts, etc. See, forexample, FIG. 53, where prosthesis 2500 is shown attached to naturalvertebra 2005 with rods 2146 which pass through, and snap intoengagement with, prosthetic pedicles 2515.

Having thus described preferred embodiments of the invention withreference to the accompanying drawings, it is to be understood that theembodiments shown herein are provided by way of example only, and thatvarious changes and modifications may be effected by one skilled in theart without departing from the scope or spirit of the invention asdefined in the claims.

1. A method for replacing a portion of a mammalian spine comprising aspinal motion segment comprising a vertebra, the method comprising:implanting an artificial disc adjacent to the vertebra to incorporatethe artificial disc into the spinal motion segment; and implanting aprosthesis on the vertebra such that the prosthesis is discrete from theartificial disc, to incorporate the prosthesis into the spinal motionsegment; wherein the artificial disc and the prosthesis are configuredfor complementary interoperation to restore natural biomechanics of thespinal motion segment.
 2. The method of claim 1, wherein the artificialdisc comprises opposing end plates and articulating structuretherebetween.
 3. The method of claim 1, wherein the artificial disccomprises opposing end plates and a deformable structure disposedbetween the opposing end plates, wherein the deformable structure isselected from the group consisting of an elastomeric body and a polymerbody.
 4. The method of claim 1, wherein implanting the prosthesis on thevertebra comprises replacing at least a portion of a facet of thevertebra.
 5. A method for replacing a portion of a mammalian spinecomprising a spinal motion segment comprising a vertebra, the methodcomprising: implanting an artificial disc adjacent to the vertebra toincorporate the artificial disc into the spinal motion segment; andimplanting a prosthesis on the vertebra such that the prosthesis isdiscrete from the artificial disc, to incorporate the prosthesis intothe spinal motion segment, the prosthesis comprising an articularsurface that replicates a natural articular surface of a vertebralfacet; wherein the artificial disc and the prosthesis are configured forcomplementary interoperation to restore natural biomechanics of thespinal motion segment, wherein the artificial disc restores articulationbetween vertebral bodies of the vertebrae, the prosthesis articulateswith another facet, no portion of the prosthesis contacts a posteriorarch of the vertebrae.
 6. The method of claim 5, wherein the artificialdisc comprises opposing end plates and articulating structuretherebetween.
 7. The method of claim 5, wherein the artificial disccomprises opposing end plates and a deformable structure disposedbetween the opposing end plates, wherein the deformable structure isselected from the group consisting of an elastomeric body and a polymerbody.
 8. The method of claim 5, wherein implanting the prosthesis on thevertebra comprises replacing at least a portion of a facet of thevertebra.
 9. A method for replacing a portion of a mammalian spine, themethod comprising: positioning an artificial disc between two adjacentvertebrae, the artificial disc comprising opposing end plates, whereinthe end plates are movable relative to each other; removing a superiorfacet and replacing the superior facet with a first prosthesis, thefirst prosthesis comprising a first articular surface that replicates anatural articular surface of the superior facet; removing an inferiorfacet and replacing the inferior facet with a second prosthesis, thesecond prosthesis comprising a second articular surface that replicatesa natural articular surface of the inferior facet, the inferior facetforming a joint with the superior facet; and restoring articulationbetween the vertebral bodies of the vertebrae, wherein the firstprosthesis, second prosthesis, and the artificial disc are operativelyconnected to restore natural biomechanics of the two adjacent vertebrae.10. The method of claim 9, wherein the method further comprises the stepof providing an articulating structure disposed between the opposing endplates of the artificial disc.